Cooling apparatus for casting mold and cooling method for casting mold

ABSTRACT

A cooling apparatus  1  cools a casting mold K with a refrigerant circulating in a refrigerant passage pipe  2  and comprises an expansion tank  3  for pressurizing the refrigerant to a pressure at which the refrigerant has a set boiling temperature T0 at which the refrigerant boils, a mold cooling section  4  inside the casting mold K for cooling the casting mold K through vaporization heat of the refrigerant boiling, an orifice portion  5  that is formed upstream of the mold cooling section  4,  a pump  6  that is attached downstream of the expansion tank  3  and upstream of the orifice portion and pumps out the refrigerant pressurized by the pressurizing unit to the orifice portion, and a heating device  7  attached downstream of the pump  6  and upstream of the orifice portion  5  for heating the refrigerant to a temperature T2 close to the set boiling temperature T0.

FIELD OF THE INVENTION

The present invention relates to a cooling apparatus for a casting mold and a cooling method for the casting mold.

DESCRIPTION OF THE RELATED ART Conventional casting molds have refrigerant passage pipes inside the mold. When metal is cast, the temperature of the mold is controlled in such a way that melted metal filling the mold is cooled appropriately to have a good cast metal product produced. Such a refrigerant as water or oil is used for cooling the inside of the mold and boiling heat transfer is utilized in order to transmit heat from the mold to the refrigerant. Japanese unexamined patent publication No. 63-157751 discloses a mold temperature control method to set a boiling temperature of a refrigerant to a predetermined temperature and subsequently cool with vaporization heat of a refrigerant the mold, in which a cooling chamber filled with the refrigerant is formed and connected with a refrigerant cooling device disposed outside the mold through pipes so that there is formed a closed circuit of the refrigerant flowing between the cooling chamber and the refrigerant cooling device, when the temperature of the refrigerant becomes higher than or equal to a predetermined boiling temperature of the refrigerant while the temperature of the mold is changing due to the casting process being under way.

SUMMARY OF THE INVENTION

It is difficult to cool the mold through boiling heat transfer while the refrigerant flowing in the refrigerant passage pipe in the mold is at a relatively low temperature because it takes some time for the refrigerant to receive heat through the mold from the melted metal and boil. In addition, there is a risk for deterioration of the mold due to a defect such as a crack being formed in the mold or the mold cracking due to a heat shock applied to the mold if there is a large temperature difference in the mold between the cavity for casting and the refrigerant passage pipe. On the other hand, if the refrigerant heated in advance to a temperature close to a boiling temperature of the refrigerant is supplied into the refrigerant passage pipe in the mold, the refrigerant can be boiled relatively quickly and the mold can be cooled through boiling heat transfer in a relatively short time. In this case, the deterioration of the mold is suppressed because the temperature difference in the mold is smaller.

However, if the refrigerant is heated with a hot heater of a heating unit disposed outside the mold so that the refrigerant at a temperature close to its boiling temperature flows in the refrigerant passage pipe in the mold, part of the refrigerant can be heated above its boiling temperature by the heating unit and a water hammer phenomenon can occur, which leads to there being a risk for the refrigerant passage pipe deteriorating due to the shock applied to the refrigerant passage pipe.

The present invention has been created to solve the above mentioned problems and is intended to provide a cooling apparatus for a casting mold and a cooling method for the casting mold which enable supplying refrigerant close to its boiling temperature into the casting mold to cool the casting mold efficiently while suppressing deterioration of the casting mold.

A cooling apparatus for a casting mold of the present invention is configured to cool the casting mold with a refrigerant flowing in a refrigerant passage pipe. This cooling apparatus has a feature to comprise; a pressurizing unit for pressurizing the refrigerant to a pressure at which the refrigerant has a set boiling temperature preset at which the refrigerant boils; a mold cooling section that is formed inside the casting mold and cools the casting mold through vaporization heat of the refrigerant boiling through heat transmitted from the casting mold; an orifice portion that is formed upstream of the mold cooling section and configured to increase a pipe pressure loss of the refrigerant passage pipe, a pump that is attached downstream of the pressurizing unit and upstream of the orifice portion and pumps out the refrigerant pressurized by the pressurizing unit to the orifice portion; and a heating device attached downstream of the pump and upstream of the orifice portion for heating the refrigerant to a temperature close to the set boiling temperature.

A cooling method of the present invention for a casting mold is configured to cool the casting mold with a refrigerant circulating through a refrigerant passage pipe inclusive of an orifice portion in which a pipe pressure loss is increased and a mold cooling section formed inside the casting mold. This cooling method has a feature to comprise; a pressurizing process of pressurizing the refrigerant to a pressure at which the refrigerant boils at a set boiling temperature that is set in advance; a pumping-out process of pumping out the pressurized refrigerant toward the orifice portion; a heating process of heating the pressurized refrigerant flowing upstream of the orifice portion to a temperature close to the set boiling temperature; and a mold cooling process of cooling the casting mold through vaporization heat generated from the refrigerant boiling in the mold cooling section after flowing through the orifice portion.

According to these configurations, the refrigerant is pressurized to a pressure at which the refrigerant boils at a set boiling temperature (pressurizing process), heated to a temperature close to the set boiling temperature and supplied into the mold cooling section formed inside the casting mold (heating process). As a result, the refrigerant is heated to quickly boil by the heat transmitted from the casting mold and the casting mold is efficiently heated by vaporization heat generated from the refrigerant (mold cooling process).

In addition, since the pressurized refrigerant is pumped out by a pump to an orifice portion that is formed upstream of the mold cooling section in the refrigerant passage pipe and to increase a pipe pressure loss (pumping-out process), the pressure of the refrigerant is higher in the refrigerant passage pipe between the pump and the orifice portion than the pressure of the refrigerant pressurized by the pressurizing unit. Therefore, the boiling temperature of the refrigerant in the refrigerant passage pipe between the pump and the orifice portion becomes higher than the set boiling temperature and the refrigerant does not partially or instantaneously boil if it is heated by the heating unit to the temperature close to the set boiling temperature. As a result, such a destructive phenomenon as water hammer hardly occurs, which results in suppressing deterioration of the refrigerant passage pipe.

The cooling apparatus for the casting mold of the present invention preferably further comprises; a refrigerant temperature meter for measuring a temperature of the refrigerant supplied into the mold cooling section; and a control unit for controlling the pressurizing unit in such a way that the set boiling temperature becomes higher if the temperature of the refrigerant measured by the refrigerant temperature meter becomes higher than the set boiling temperature.

The cooling method for a casting mold of the present invention preferably further comprises an additional pressurizing process of pressurizing the refrigerant so as to make the set boiling temperature become higher if a measured temperature of the refrigerant in the mold cooling section is higher than the set boiling temperature.

According to these configurations, if the temperature of the refrigerant supplied into the mold cooling section that is measured by the refrigerant temperature meter becomes higher than the set boiling temperature, the set boiling temperature is made to be higher by the controlling the pressurizing unit and boiling heat transfer is maintained. That is, if the temperature of the refrigerant in the mold cooling section becomes too high, the refrigerant becomes fully evaporated (so-called dry-out condition) and the evaporated refrigerant flows, which results in no boiling heat transfer occurring. It is possible to have the boiling heat transfer going on by making the set boiling temperature of the refrigerant higher and controlling the timing when the refrigerant evaporates.

The present invention provides a cooling apparatus for the casting mold and a cooling method for a casting mold that enable improving the cooling effect for cooling the casting mold by supplying inside the casting mold the refrigerant that is heated to a temperature close to the boiling temperature and suppressing deterioration of the casting mold and the refrigerant passage pipe at the same time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a configuration of a cooling apparatus for a casting mold of an embodiment of the present invention.

FIG. 2 schematically shows a configuration of an expansion tank of a sealed type.

FIG. 3 schematically shows a configuration of a modified example of the expansion tank.

FIG. 4A schematically shows an orifice portion of an embodiment.

FIG. 4B schematically shows a first modified example of the orifice portion.

FIG. 4C schematically shows a second modified example of the orifice portion.

FIG. 5 is a figure explaining changes in a flow rate, a pressure and a temperature of the refrigerant at various sections of the cooling apparatus for the casting mold when the refrigerant is flowing through the various sections.

DETAILED DESCRIPTION OF THE EMBODIMENT

Embodiments of the present invention are explained in detail with reference to FIG. 1 to FIG. 5. In the explanation to be given, each sign is used to stand for elements which are the same as each other and a duplicated explanation is skipped.

FIG. 1 is a schematic diagram showing a configuration of a cooling apparatus for a casting mold of an embodiment of the present invention. It should be noted that a part of a casting mold K is drawn with virtual lines (double dotted lines).

As shown in FIG. 1, a cooling apparatus 1 for a casting mold is an apparatus to cool the casting mold K with vaporization heat of refrigerant circulating through a refrigerant passage pipe 2 that constituting a closed circuit.

The cooling apparatus 1 for the casting mold comprises an expansion tank 3 that corresponds to a pressurizing unit to pressurize the refrigerant, a mold cooling section 4 to cool a casting mold K, an orifice portion 5 to increase a pipe pressure loss in the refrigerant passage pipe 2, a pump 6 to circulate the refrigerant, a heating device 7 to heat the refrigerant and a cooling device 8 to cool the refrigerant. The expansion tank 3, the mold cooling section 4, the orifice portion 5 and the pump 6 are interposed in the refrigerant passage pipe 2. The heating device 7 and the cooling device 8 are attached on the refrigerant passage pipe 2. The cooling apparatus 1 for the casting mold further comprises a temperature meter 41 to measure a temperature of the refrigerant in the mold cooling section and a control unit 9 to have control over the expansion tank 3.

The casting mold K to be cooled is a mold for casting such a metal product as an engine block and has an cavity Ka of a space into which melted metal is poured and a mold cooling section 4 of a passage through which the refrigerant flows. A kind of the melted metal is not restricted to a particular metal may be any kind of metal such as iron, aluminum and copper. For example, when the melted metal is of aluminum or an aluminum alloy, a temperature of the melted metal is approximately between 720° C. and 750° C. (above its melting temperature, 660° C.). Usually a cast product is taken off from the mold when the temperature of the mold lowers to 300° C.

The refrigerant passage pipe 2 is a circular-shaped pipe through which pressurized refrigerant circulates and comprises the mold cooling section 4 which is a pipe-shaped space that is formed inside the casting mold K and a pipe 21 disposed running outside the casting mold K. A downstream end portion 21 a of a pipe 21 is connected with an upstream end 4 a of the mold cooling section 4 through the orifice portion 5 to be explained below. An upstream end 21 b of the pipe 21 is connected with a downstream end portion 4 b of the mold cooling section 4. The pipe 21 and the mold cooling section 4 constitute a closed circuit passage for the refrigerant.

The expansion tank 3 is a pressure vessel in which the pressurized refrigerant is stored. The expansion tank 3 has a function of pressurizing the stored refrigerant to a pressure (set pressure) at which the stored refrigerant boils at a predetermined boiling temperature. The expansion tank 3 is, for example, a sealed expansion tank as shown in FIG. 2. If water is used for the refrigerant, the predetermined boiling temperature of the refrigerant is changed approximately within a temperature range between 160° C. and 180° C. by changing the pressure approximately within a pressure range between 0.5 MPa and 0.9 MPa. As a result, the refrigerant which flows from downstream of the orifice portion 5 to upstream of the pump 6 is pressurized to the predetermined pressure.

FIG. 2 schematically shows a configuration of an expansion tank of a sealed type. As shown in FIG. 2, the sealed expansion tank 3 is divided into a liquid space 32 and a gas space 33 which borders on a liquid surface 31. The liquid surface 31 goes up and down so that a pressure of the gas space 33 is kept equal to a pressure of the liquid space 32. The liquid space 32 is filled with the refrigerant and in communication with the refrigerant passage pipe 2. The gas space 33 is connected with a high pressure cylinder 34 and is filled with a compressed gas whose pressure is equal to or higher than a set pressure of the refrigerant. There is a pressure meter 35 that is attached on the gas space and configured to measure a pressure of the compressed gas in the gas space 33, which corresponds to the set pressure of the refrigerant. There is a flow regulator valve 36 interposed in a pipe 34 a through which the gas space 33 and the high pressure cylinder 34 are made to be in communication with each other. There is a purge valve 37 attached on the gas space 33. Each of the pressure meter 35, the flow regulator valve 36 and the purge valve 37 is connected with a control unit 9 so that opening degrees of the flow regulator valve 36 and the purge valve 37 are controlled based on a measured value of the pressure meter 35. As a result, the refrigerant is pressurized to the set pressure.

The structure of the expansion tank 3 is not limited to the above mentioned one and whatever structure may be used as long as it is capable of pressurizing the refrigerant to the set pressure. For example, an expansion tank 3 (pressurizing means) having such a mechanically pressurizing mechanism shown in FIG. 3 as to pressurize the refrigerant with a piston of a pressure plate 39 pushed by a spring 38.

As shown in FIG. 1, the mold cooling section 4 is a flow passage (space) formed in the casting mold K and is a part of the refrigerant passage pipe 2. The mold cooling section 4 has a function of cooling the casting mold K that is heated to a high temperature by a heat of the melted metal poured into the cavity Ka. The refrigerant heated by the heating device 7 to a temperature close to its boiling temperature is supplied to the mold cooling section 4. Since the refrigerant supplied to the mold cooling section 4 boils relatively quickly due to the heat from the casting mold K, the casting mold K is efficiently cooled by the vaporization heat of the refrigerant. The mold cooling section 4 has a temperature meter 41 as a refrigerant temperature detecting devices to measure the temperature of the refrigerant. The temperature meter 41 outputs a measured temperature to the control unit 9.

The orifice portion 5 is configured to increase a pipe pressure loss in a part of the refrigerant passage pipe 2 and disposed upstream of the mold cooling section 4. The orifice portion 5 comprises a small diameter portion 51 of which a pipe diameter is smaller than the pipe 21 and a tapered portion 52 which is in a tapered shape and formed between the pipe 21 and the small diameter portion 51 and the diameter of the tapered portion 52 becomes smaller toward the small diameter portion 51. The small diameter portion 51 is inserted into an upstream end portion 4 a of the mold cooling section 4 that is formed inside the casting mold K. The small diameter portion 51 has an inner diameter of 0.5 mm to 6.0 mm, for example. The tapered portion 52 is jointed with a downstream end 21 a.

The shape of orifice portion 5 is not limited to one shown in FIG. 4A and may be in any shape as long as it has function to increase the pipe pressure loss in the refrigerant passage pipe 2. For example, a first modified example as shown in FIG. 4B may be used and corresponds to an orifice portion 5 that is configured to have an opening 55 formed to have an diameter smaller than the inner diameter of the pipe 21 inserted into the upstream end portion 4 a of the mold cooling section 4. In addition, a second modified example as shown in FIG. 4C may be used and corresponds to the orifice portion 5 that is configured to include a flow regulator valve 53 interposed between the small diameter portion 52 and the pipe 21 to make smaller a cross section of the flow passage.

As shown in FIG. 1, the pump 6 is configured to pressurize the refrigerant and circulate the pressurized refrigerant through the refrigerant passage pipe 2. The pump 6 is installed upstream of the orifice portion 5 and downstream of the expansion tank 3 and sends out the pressurized refrigerant to the orifice portion 5. The pipe pressure loss is higher in the part of the refrigerant passage pipe 2 between the pump 6 and the orifice portion 5 than in the other parts of the refrigerant passage pipe 2. As a result, the refrigerant in the part of the refrigerant passage pipe 2 between the pump 6 and the orifice 5 has a higher pressure than the set pressure by a pressure corresponding to a lifting height of the pump 6 and has a boiling temperature higher than the set boiling temperature.

The heating device 7 is configured to heat the refrigerant to a temperature close to the set boiling temperature and installed upstream of the orifice portion 5 and downstream of the pump 6. Specifically, the heating device 7 comprises a heater 71, a first circulation pipe 72 through which a heating medium heated by the heater 71 circulates and a first heat exchange section 73 where heat is exchanged between the refrigerant and the heating medium. The heater 71 heats a part of the first circulation pipe 72 which is disposed on the other side of the first heat exchange section 73, in order to have the heating medium heated to a predetermined temperature. The first heat exchange section 73 is configured to have a part of the refrigerant passage pipe 2 in contact with the part of the first circulation pipe 72 so that heat is transferred from the heating medium circulating in the first circulation pipe 72 to the refrigerant flowing in the refrigerant passage pipe 2. The refrigerant is heated to a temperature close to the set boiling temperature. For example, when water is used for the refrigerant and the set boiling temperature is 170° C., the refrigerant should be heated by the heating device 7 between 140° C. and 150° C. As has been mentioned, since the refrigerant between the pump 6 and the orifice portion 5 is pressurized to a higher pressure than the set pressure, the refrigerant does not boil partially or at once when it is heated by the heating device to the temperature close to the set boiling temperature. Therefore, such a destructive phenomenon as a water hammer is prevented from occurring. The refrigerant heated by the heating device 7 to the temperature close to the set boiling temperature is made to flow through the orifice portion 5 and supplied into the mold cooling section 4. The pressure of the refrigerant after passing the orifice portion 5 lowers to the set pressure.

The cooling device 8 is configured to cool the refrigerant to a predetermined temperature lower than the set boiling temperature and attached downstream of the mold cooling section 4. The cooling device 8 comprises a second circulation pipe 81 through which other refrigerant than one flowing in the refrigerant passage pipe 2 circulates and a second heat exchange section 82 where heat is transferred from the refrigerant flowing in the refrigerant passage pipe 2 to the other refrigerant flowing in the second circulation pipe 81. A cooling unit, which is not shown in FIG. 1, is attached on a part of the second circulation pipe 81 that is the other side of the second heat exchange section 82 and configured to cool the other refrigerant flowing through the part of the second circulation pipe 81. The second heat exchange section 82 is configured to have a part of the refrigerant passage pipe 2 in contact with the part of the second circulation pipe 81. The refrigerant flowing in the refrigerant passage pipe 2, which is in a single gas phase flow or a double phase flow after boiled in the mold cooling section 4, comes into the second heat exchange section 82, where the refrigerant is cooled to be condensed to return liquid.

As shown in FIG. 2, the control unit 9 controls a pressure at which the refrigerant in the expansion tank 3 is pressurized. The control unit 9 functions as a computer to have a CPU (Central Processing Unit) execute a control program stored in a storage device such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and is configured to perform a predetermined control procedure. The control unit 9 is connected with the pressure meter 35, the flow regulator valve 36, the purge valve 37 and the temperature meter 41. For example, the control unit 9 controls the flow regulator valve 36 and the purge valve 37 in such a way that the refrigerant has the set pressure at which the refrigerant boils at the set boiling temperature. If a measured value on the temperature meter 41 is higher than the set boiling temperature, the control unit 9 controls the flow regulator valve 36 and the purge valve 37 in such a way that the set boiling temperature becomes higher.

The cooling apparatus 1 for the casting mold K is, in principle, configured as above mentioned. Next, an explanation is given on operation of the cooling apparatus 1 for the casting mold K with reference to FIG. 5.

FIG. 5 is a figure explaining changes in a flow rate, a pressure and a temperature of the refrigerant at various sections of the cooling apparatus for the casting mold when the refrigerant is flowing through the various sections.

<Pressurizing Process>

As shown in FIG. 5, the refrigerant flowing in the refrigerant passage pipe 2 is pressurized in the expansion tank 3 to the set pressure P1 so that the refrigerant boils at the set boiling temperature T0. To be specific, the refrigerant is pressurized to the set pressure P1 by the control unit 9 changing opening degrees of the flow regulator valve 36 and the purge valve 37 based on the measured pressure value on the pressure meter 35. The initial temperature of the refrigerant pressurized in the expansion tank 3 is T1 (T1<T0).

<Pumping-Out Process>

The pressurized refrigerant in the expansion tank 3 is pumped out to the orifice portion 5. Since the refrigerant passage pipe 2 has the orifice portion 5 in which the pipe pressure loss becomes higher, the pressure of the refrigerant between the orifice portion 5 and the pump 6 is higher than the set pressure P1 by the pressure corresponding to the lifting height of the pump 6.

The refrigerant is heated to a temperature T2 close to the set boiling temperature T0 by the heating device 7 that is attached between the pump 6 and the orifice portion 5. Since the refrigerant between the pump 6 and the orifice portion 5 is pressurized to a pressure P2 that is higher than the set pressure P1, the refrigerant flowing in the heating device 7 does not boil if the refrigerant is heated by the heating device partially or instantaneously above the set boiling temperature T0. Therefore, a water hammer phenomenon due to the refrigerant boiling is prevented, which leads to prevention of the refrigerant passage pipe 2 from deteriorating through reduction of an impact applied on the refrigerant passage pipe 2.

<Mold Cooling Process>

After the refrigerant passes the orifice portion 5, the pressure of the refrigerant heated to the temperature T2 close to the set temperature T0 lowers to the set pressure P1 and the refrigerant is supplied into the mold cooling section 4. The refrigerant in the mold cooling section 4 receives heat from the casting mold K, is heated to a temperature T3 which is equal to the set boiling temperature T0 and boils. The refrigerant in the mold cooling section 4 keeps on boiling and the casting mold K is efficiently cooled through boiling heat transfer using vaporization heat generated on the refrigerant boiling.

<Cooling Process>

The refrigerant becomes in a single phase of gas or a double phase of gas and liquid after passing the mold cooling section 4 and is supplied to the cooling device 8. Then, the refrigerant is cooled by the cooling device 8 to the initial temperature T1, becomes liquid and recirculates through the expansion tank 3 and the pump 6. It should be noted that the flow rate of the refrigerant Q1 is constant over the entire circulation passage.

<Additional Pressurizing Process>

As is indicated in FIG. 1 and FIG. 2, the control unit 9 controls the pressure applied to the refrigerant in the expansion tank 3 based on the measured temperature value by the temperature meter 41 of the refrigerant supplied into the mold cooling section 4. To be specific, the control unit 9 calculates a temperature difference (T0−T3) between the set boiling temperature T0 that is set in advance and a refrigerant temperature T3 measured by the temperature meter 41, and if the temperature difference (T0−T3) is negative (the refrigerant temperature exceeds the set boiling temperature), a new boiling temperature T0′ that is higher than T0 (T0′>T0) is set anew and the flow regulator valve 36 and the purge valve 37 both attached on the expansion tank 3 are adjusted in such a way that the refrigerant is pressurized to a newly set pressure P1′ corresponding to the newly set boiling temperature T0′.

In other words, if the refrigerant temperature T3 in the mold cooling section 4 is higher than the set boiling temperature T0, the refrigerant, being in a completely vaporized condition, that is to say, a dry-out condition, flows in the mold cooling section 4. When the refrigerant is in the dry-out condition, there is no cooling effect through vaporization heat because the refrigerant is completely vaporized and the casting mold K cannot be cooled efficiently. Therefore, if the set boiling temperature is temporarily made higher, the refrigerant is not in the dry-out condition and the casting mold K can be cooled efficiently through vaporization heat. After the casting mold K is cooled sufficiently through vaporization heat, the newly set boiling temperature T0′ is lowered to the initial set boiling temperature T0 (set pressure) and the casting mold K is more efficiently cooled without the refrigerant being in the dry-out condition.

As has been explained, according to the cooling apparatus 1 for the casting mold of the present embodiment, the refrigerant, being pressurized in the expansion tank 3 to boil at the set boiling temperature T0, is heated by the heating device 7 to a temperature T2 close to the set boiling temperature T0 and supplied into the mold cooling section 4 that is formed inside the casting mold K. As a result, the refrigerant becomes in the boiling condition due to the heat from the casting mold K and the casting mold is cooled efficiently through vaporization heat. In addition, since the refrigerant heated to the temperature T2 close to the set boiling temperature T0 is supplied into the mold cooling section 4, a temperature difference in the casting mold K between a side on the cavity Ka and a side on mold cooling section 4 is relatively small and a thermal shock applied to the casting mold is made smaller.

In addition, the pressurized refrigerant is pumped out to the orifice portion 5 that is formed upstream of the mold cooling section 4 and configured to increase a pipe pressure loss and the pressure P2 of the refrigerant in the refrigerant passage pipe 2 between the pump 6 and the orifice portion 5 is higher than the pressure P1 of the refrigerant in the mold cooling section 4. As a result, since the boiling temperature of the refrigerant between the pump 6 and the orifice portion 5 is higher than the set boiling temperature T0, the refrigerant does not boil partially or instantaneously when it is heated by the heating device 7 attached between the pump 6 and the orifice portion 5 to the temperature T2 close to the set boiling temperature T0. Therefore, a destructive phenomenon such as a water hammer does not easily occur and the refrigerant passage pipe is prevented from deteriorating. In addition, the refrigerant temperature is easily controlled by the heating device 7.

Moreover, according to the cooling apparatus 1 for the casting mold of the present embodiment, since the expansion tank 3 is controlled in such a way that the set boiling temperature T0 becomes higher when the refrigerant temperature T3 measured with the temperature meter 41 becomes higher than the set boiling T0.

Although the embodiment of the present invention has been explained with reference to the figures, it should be noted that the present invention is not limited to the embodiment explained and that there should be other embodiments which are within the scope of the present invention.

For example, though water is used in the present embodiment, the present invention is not limited to embodiments using water and other liquid such as oil may be used.

The present embodiment has the refrigerant passage pipe 2 that is a closed circuit pipe, However the refrigerant passage pipe 2 may be of a open circuit pipe as long as the pressurized refrigerant is supplied into the refrigerant passage pipe 2.

Furthermore, the present embodiment has the cooling device 8 downstream of the mold cooling section 4 and the present invention is not limited to this configuration. For example, the refrigerant may be discharged out of the refrigerant passage pipe 2 that is of an open circuit pipe. The cooling device is not needed in this configuration. 

What is claimed is:
 1. A cooling apparatus for a casting mold to cool the casting mold with a refrigerant flowing in a refrigerant passage pipe comprising; a pressurizing unit for pressurizing the refrigerant to a pressure at which the refrigerant has a set boiling temperature preset at which the refrigerant boils; a mold cooling section that is formed inside the casting mold and cools the casting mold through vaporization heat of the refrigerant boiling through heat transmitted from the casting mold; an orifice portion that is formed upstream of the mold cooling section and configured to increase a pipe pressure loss of the refrigerant passage pipe, a pump that is attached downstream of the pressurizing unit and upstream of the orifice portion and pumps out the refrigerant pressurized by the pressurizing unit to the orifice portion; and a heating device attached downstream of the pump and upstream of the orifice portion for heating the refrigerant to a temperature close to the set boiling temperature.
 2. The cooling apparatus for the casting mold as described in claim 1 further comprising; a refrigerant temperature meter for measuring a temperature of the refrigerant supplied into the mold cooling section; and a control unit for controlling the pressurizing unit in such a way that the set boiling temperature becomes higher if the temperature of the refrigerant measured by the refrigerant temperature meter becomes higher than the set boiling temperature.
 3. A cooling method for a casting mold with a refrigerant circulating through a refrigerant passage pipe inclusive of an orifice portion in which a pipe pressure loss is increased and a mold cooling section formed inside the casting mold, the cooling method comprising; a pressurizing process of pressurizing the refrigerant to a pressure at which the refrigerant boils at a set boiling temperature that is set in advance; a pumping-out process of pumping out the pressurized refrigerant toward the orifice portion; a heating process of heating the pressurized refrigerant flowing upstream of the orifice portion to a temperature close to the set boiling temperature; and a mold cooling process of cooling the casting mold through vaporization heat generated from the refrigerant boiling in the mold cooling section after flowing through the orifice portion.
 4. The cooling method for a casting mold as described in claim 3 further comprising an additional pressurizing process of pressurizing the refrigerant so as to make the set boiling temperature become higher if a measured temperature of the refrigerant in the mold cooling section is higher than the set boiling temperature. 